The statement "some English language 'Irish ballads' are descendents of old English ballads" is literally quite correct. (You would have to add Scots ballads to that also.) But which ballads? Certainly, there is nothing in the old broadside copies of "The Wild Rover" I've viewed that makes the song unequivocably English or Irish or any nationality. Yes, many songs are known in a few countries with the origin long obscured. "The Cruel Mother" is not indigenous to Ireland but "The Wild Rover?" I don't think you can say where "The Wild Rover" originated. I agree with Martin Ryan that's it's just great it did survive - even if it is done to death. God bless those broadside hawkers!

Regarding the Irish languague, I'm looking at a map of the distribution of Irish speakers in Ireland in 1851. It shows that more than 75% of the population were not Irish speakers in an area to the east of a line roughly from Letterkenny, through Roscommon Town to Limerick City, and through Kilkenny to Waterford. I have nothing older than that but it is interesing however.

Now, about "Tim Finegan's Wake" - did you know it was written in New York City?

All the best,
Dan